1. Field of the Invention
The present invention relates to chemical sensors, including biosensors, used in medical and health diagnoses and food testing.
2. Related Background Art
In recent years, the demand for medical diagnosis and food testing has been escalating, and the development of a compact, high-speed sensing, low-cost biosensors is sought. To this end, biosensors utilizing electrochemical methods with electrodes and FET have been made through an application of semiconductor processing technology.
However, further integration, lower cost and sensors compatible with any measuring environment are sought, and a biosensor that uses surface plasmon resonance as a transducer is considered promising to meet these demands. Such a biosensor would make use of surface plasmon resonance that is generated on a metallic thin film provided on the surface of total-reflection prism to detect whether a substance is adsorbed, such as whether an antigen is adsorbed in an antigen-antibody reaction.
Recently, a localized plasmon resonance sensor that uses metal fine particles has been proposed to achieve a highly sensitive sensing. In the localized plasmon resonance sensor, changes in the medium in vicinity of the metal fine particles are detected by irradiating a light on a substrate to which metal fine particles are fixed and measuring the absorbancy of the light transmitted through the metal fine particles.
In conventional localized plasmon resonance sensors that use metal fine particles, a film of metal fine particles is formed on a substrate by using a metal colloidal solution; however, this entails a difficulty in gaining a uniformity in the size of metal fine particles in the metal colloidal solution within a deviation of 10˜20%. In addition, due to the fact that the substrate is simply immersed in the metal colloidal solution, the arrangement of the metal fine particles on the substrate is completely random, so that neither the interval between the metal fine particles nor the arrangement direction of the metal fine particles can be controlled.
As a result, the width of absorbancy spectrum in such sensors is wide, which lowers the peak intensity; this causes changes in signals that detect changes in the medium in the vicinity of the metal fine particles to be low, which in turn causes the sensitivity of the sensor to be limited.